public class FileSplitter {
private static final int BUFSIZE = 4*1024;
public boolean needsSplitting(String file, int chunkSize) {
return new File(file).length() > chunkSize;
}
private static boolean isASplitFileChunk(String file) {
return chunkIndexLen(file) > 0;
}
private static int chunkIndexLen(String file) {
int n = numberOfTrailingDigits(file);
if (n > 0) {
String zeroes = new String(new char[n]).replace("\0", "0");
if (file.matches(".*\\.part[0-9]{"+n+"}?of[0-9]{"+n+"}?$") && !file.endsWith(zeroes) && !chunkNumberStr(file, n).equals(zeroes)) {
return n;
}
}
return 0;
}
private static String getWholeFileName(String chunkName) {
int n = chunkIndexLen(chunkName);
if (n>0) {
return chunkName.substring(0, chunkName.length() - 7 - 2*n); // 7+2n: 1+4+n+2+n : .part012of345
}
return chunkName;
}
private static int getNumberOfChunks(String filename) {
int n = chunkIndexLen(filename);
if (n > 0) {
try {
String digits = chunksTotalStr(filename, n);
return Integer.parseInt(digits);
} catch (NumberFormatException x) { // should never happen
}
}
return 1;
}
private static int getChunkNumber(String filename) {
int n = chunkIndexLen(filename);
if (n > 0) {
try {
// filename.part001of200
String digits = chunkNumberStr(filename, n);
return Integer.parseInt(digits)-1;
} catch (NumberFormatException x) {
}
}
return 0;
}
private static int numberOfTrailingDigits(String s) {
int n=0, l=s.length()-1;
while (l>=0 && Character.isDigit(s.charAt(l))) {
n++; l--;
}
return n;
}
private static String chunksTotalStr(String filename, int chunkIndexLen) {
return filename.substring(filename.length()-chunkIndexLen);
}
protected static String chunkNumberStr(String filename, int chunkIndexLen) {
int p = filename.length() - 2 - 2*chunkIndexLen; // 123of456
return filename.substring(p,p+chunkIndexLen);
}
// 0,8 ==> part1of8; 7,8 ==> part8of8
private static String chunkFileName(String filename, int n, int total, int chunkIndexLength) {
return filename+String.format(".part%0"+chunkIndexLength+"dof%0"+chunkIndexLength+"d", n+1, total);
}
public static String[] splitFile(String fname, long chunkSize) throws IOException {
FileInputStream fis = null;
ArrayList<String> res = new ArrayList<String>();
byte[] buffer = new byte[BUFSIZE];
try {
long totalSize = new File(fname).length();
int nChunks = (int) ((totalSize + chunkSize - 1) / chunkSize);
int chunkIndexLength = String.format("%d", nChunks).length();
fis = new FileInputStream(fname);
long written = 0;
for (int i=0; written<totalSize; i++) {
String chunkFName = chunkFileName(fname, i, nChunks, chunkIndexLength);
FileOutputStream fos = new FileOutputStream(chunkFName);
try {
written += copyStream(fis, buffer, fos, chunkSize);
} finally {
Closer.closeSilently(fos);
}
res.add(chunkFName);
}
} finally {
Closer.closeSilently(fis);
}
return res.toArray(new String[0]);
}
public static boolean canJoinFile(String chunkName) {
int n = chunkIndexLen(chunkName);
if (n>0) {
int nChunks = getNumberOfChunks(chunkName);
String filename = getWholeFileName(chunkName);
for (int i=0; i<nChunks; i++) {
if (!new File(chunkFileName(filename, i, nChunks, n)).exists()) {
return false;
}
}
return true;
}
return false;
}
public static void joinChunks(String chunkName) throws IOException {
int n = chunkIndexLen(chunkName);
if (n>0) {
int nChunks = getNumberOfChunks(chunkName);
String filename = getWholeFileName(chunkName);
byte[] buffer = new byte[BUFSIZE];
FileOutputStream fos = new FileOutputStream(filename);
try {
for (int i=0; i<nChunks; i++) {
FileInputStream fis = new FileInputStream(chunkFileName(filename, i, nChunks, n));
try {
copyStream(fis, buffer, fos, -1);
} finally {
Closer.closeSilently(fis);
}
}
} finally {
Closer.closeSilently(fos);
}
}
}
public static boolean deleteAllChunks(String chunkName) {
boolean res = true;
int n = chunkIndexLen(chunkName);
if (n>0) {
int nChunks = getNumberOfChunks(chunkName);
String filename = getWholeFileName(chunkName);
for (int i=0; i<nChunks; i++) {
File f = new File(chunkFileName(filename, i, nChunks, n));
res &= (f.delete() || !f.exists());
}
}
return res;
}
private static long copyStream(FileInputStream fis, byte[] buffer, FileOutputStream fos, long maxAmount) throws IOException {
long chunkSizeWritten;
for (chunkSizeWritten=0; chunkSizeWritten<maxAmount || maxAmount<0; ) {
int toRead = maxAmount < 0 ? buffer.length : (int)Math.min(buffer.length, maxAmount - chunkSizeWritten);
int lengthRead = fis.read(buffer, 0, toRead);
if (lengthRead < 0) {
break;
}
fos.write(buffer, 0, lengthRead);
chunkSizeWritten += lengthRead;
}
return chunkSizeWritten;
}
}
借用Closerhere或from org.apache.logging.log4j.core.util。